氨选择性催化还原(NH₃-SCR)技术需要进一步研发在相对较低温度(<300 ℃)下具有良好催化活性、高稳定性及环境友好的脱硝催化材料。本工作采用草酸共沉淀法制备Mn-Fe-O催化材料, 并对其进行不同含量CeO₂修饰, 用于低温NH₃-SCR脱硝催化反应。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气吸附-脱附、X射线光电子能谱(XPS)、程序升温还原或脱附(H₂-TPR、NH₃-TPD)等手段对催化剂进行了表征。催化结果表明, 在相同反应条件下适量CeO₂修饰后的Mn-Fe-O样品比纯Mn-Fe-O表现出更优异的NH₃-SCR脱硝催化性能, 在80 ℃时NO转化率在95%以上, 且具有较高的N₂选择性。CeO₂修饰提高了Mn-Fe-O氧化物表面的Fe ³⁺、Mn ³⁺和Mn ⁴⁺含量及表面酸性位点数量, 从而有助于NH₃的吸附及催化反应的进行, 并且Fe ²⁺/Fe ³⁺、Mn ²⁺/Mn ³⁺/Mn ⁴⁺以及Ce ³⁺/Ce ⁴⁺电子对之间的相互氧化还原反应提高了催化剂的氧化还原能力及稳定性。

The ammonia selective catalytic reduction (NH₃-SCR) technology is still necessary to further develop denitration catalytic materials which have good catalytic activity, high stability and environmental friendliness at relatively low temperature (<300 ℃). In this work, the Mn-Fe-O catalyst was prepared by oxalate co-precipitation method and modified with different contents of CeO₂ for low temperature NH₃-SCR of NO. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption, X-ray photoelectron spectroscopy (XPS), temperature programmed reduction or desorption (H₂-TPR, NH₃-TPD). The catalytic results show that as compared with pure Mn-Fe-O sample, Mn-Fe-O modified with suitable CeO₂ content shows much better performance for NH₃-SCR with 95% conversion of NO and a high N₂ selectivity at 80 ℃ under the same reaction conditions. CeO₂ modification increases the content of Fe ³⁺, Mn ³⁺ and Mn ⁴⁺, and the number of surface acid sites on the surface of Mn-Fe-O oxide, which contribute to the adsorption of NH₃ and the catalytic reaction. In addition, redox reactions among Fe ²⁺/Fe ³⁺, Mn ²⁺/Mn ³⁺/Mn ⁴⁺ and Ce ³⁺/Ce ⁴⁺ pairs improve the redox ability and stability of the catalyst.